It’s been about seven months since Google announced their interest-based ad-targeting program, which gathers consumer behavioral information across the massive AdSense network of independent sites. Google left it up to the individual sites whether or not to participate, but Google stipulated that to do so they must provide new disclosure in their privacy policy and a link to Google’s privacy policy.

Using links to the Google’s privacy policy as a marker, I did some quick and dirty calculations in June to assess adoption. Now in October we’re in a little better position to make a guesstimate. Importantly, we now have a denominator, since Google disclosed in their Q3 2009 earnings conference call that there are at least a million sites in the AdSense network. For the numerator, each search engine provides its own count of the pages that carry the privacy policy link (and it seems reasonable to assume that in general each site carries the link only on one page):

Taking the average of Google and Yahoo!’s numbers, and assuming there are one million AdSense sites, it looks like Google’s interest-based ad targeting now reaches about one-quarter of the AdSense network. This pace of adoption seems low given the higher revenue expectations for behavioral targeting and Yahoo!’s apparent success with the technology on news sites.

Of course, ultimately it isn’t the sheer number of sites electing to be in the program that matters; it’s the traffic volume and quality of the sites that do choose to opt-in that determines the program’s success (and the scope of consumer information collected). But if three-quarters of AdSense sites are still hesitating, perhaps Google hasn’t shown them the money just quite yet.

As with so many things, only Google knows. But it may be that this slow adoption has something to do with why so few of us appear to have any advertising-worthy interests, at least according to Google’s Ad Preferences Manager. This is the transparency tool Google rolled out to soften privacy concerns about the AdSense targeting program. As explained in a prior post, few folks actually appear to have any interests available to target upon. Is there a vicious circle at work here?